We investigate how supervisors influence bank transparency through supervisory disclosures and public enforcement. Upon adoption of the Single Supervisory Mechanism (SSM) for major Eurozone banks, the European Central Bank (ECB) as the new supervisor undertook a comprehensive review of bank balance sheets and publicly disclosed the results of this Asset Quality Review (AQR). The AQR disclosures revealed what the ECB perceived to be a substantial overvaluation of bank assets, and in particular problem loans. The magnitude of the AQR adjustments varied substantially across supervised banks. We exploit this firm-level variation as well as the staggered introduction of the SSM to analyze the change in affected banks’ reporting behavior and transparency. The ECB’s preference for more conservative reporting is associated with higher levels of loan loss provisions and non-performing loan classifications in the following periods. Pointing at the role of enforcement institutions, this reporting effect is particularly pronounced for firms whose prior national supervisors were more likely to be captured by political interest. At the same time, corresponding positive liquidity effects are concentrated among SSM banks that were exposed to potential pressure from market forces. Our findings suggest that supervisory disclosures are potentially effective in establishing greater transparency of the banking sector, but depend on the presence of firm-level incentives that help establish market discipline.